An advanced television systems committee mobile/handheld (ATSC service logically shares one physical channel with standard ATSC broadcasting such as an 8-vestigial side band (VSB). The ATSC M/H service uses portion of a total bandwidth of about 19.39 megabits per second (Mbps), and provides a terrestrial broadcasting service to users of a mobile or portable TV by transmission through an internet protocol (IP) transport. That is, through time-sharing of an M/H frame of about 19.39 Mbps constructed by an 8-VSB packet and an M/H packet, the two foregoing services may be provided independently and simultaneously. Here, the 8-VSB packet is received and processed in a fixed reception environment and used for providing a standard ATSC broadcasting service. The M/H packet is received and processed by a mobile or portable receiver and used for providing an audio/video (A/V) service independently of the 8-VSB.
Thus, methods of providing the 3DTV service presupposing real-time broadcasting in an in-band transmission broadcasting environment include 1) a method of transmitting left and right image information through an 8-VSB channel, 2) a method of transmitting left and right image information through an M/H channel, and 3) a method of transmitting left and right image information through both the 8-VSB channel and the M/H channel, as shown in Table 1.
TABLE 1ScenarioHDTVSDTVMobile3DTV1. HD only Service19.2 Mbps2. HD and Mobile16.2 Mbps3 Mbps3. SDTV and 3DTV4.7 Mbps14.5 Mbps4. SDTV, Mobile and4.7 Mbps3 Mbps11.5 Mbps3DTV5. HDTV plus 3D 12 Mbps 7.2 Mbpsenhancement6. HDTV, Mobile and10.1 Mbps3 Mbps 6.1 Mbps3D enhancement7. SDTV, HDTV(AVC)4.7 Mbps14.5 Mbpsand/or 3DTV(advancedcodec)8. SDTV, Mobile,4.7 Mbps3 Mbps11.5 MbpsHDTV(AVC) and/or3DTV(advanced codec)
In a case of the method 1) in which a stereo image including a left image and a right image is transmitted through only the M/H channel, a mobile 3DTV service is available. However, it is difficult to provide image quality equivalent to a high-definition (HD) level due to a narrow bandwidth of the M/H channel.
In a case of the method 2) in which the stereo image is transmitted through only the 8-VSB channel, an HD level service may be achieved since the 8-VSB channel has a wider bandwidth than the M/H channel. At this time, the left image may be compressed by a moving picture expert group (MPEG)-2 to maintain reverse compatibility with the conventional ATSC method. However, when the left image is compressed by MPEG-2, the left image is encoded using only 62.5% or 52.6% of the bandwidth of the conventional ATSC method. Therefore, a reduction in image quality of an HDTV may often occur. For example, in Table 1 above, the 62.5% bandwidth may be used in compressing the left image by MPEG-2 without using the M/H service according to Scenario 5 of Table 1. Also, according to Scenario 6 of Table 1, 52.6% of the bandwidth may be used in compressing the left image by MPEG-2 without using the M/H service.
In addition, in a case of the method 3) in which the stereo image is transmitted through both the 8-VSB channel and the M/H channel in a dividing manner, high image quality may be achieved in comparison to the cases using only the 8-VSB channel or the H/m channel. However, due to a great difference in the bandwidth between the 8-VSB channel and the M/H channel, encoding of the right image to the HD level is difficult. Accordingly, when an HD-level stereo image is compressed and transmitted, the right image restored by an image receiver may have a lower resolution and image quality than that of the left image. As a consequence, due to a reduction in the image quality of the restored right image, a subjective image quality of a 3D stereo image generated by synthesizing the restored left image and right image would be reduced.
Therefore, there is a demand for a technology for maintaining reverse compatibility with conventional TSC 8-VSB and ATSC M/H systems while minimizing reduction in a spatio-temporal resolution of left and right images, imbalance in image quality, and reduction in image quality of a 3D stereo image, with regard to transmission of a stereo image using the 8-VSB channel and the M/H channel which are logically separated in one physical channel.